linux-kernel - Re: [PATCH v3] MM: CMA: add a simple kernel module as the helper to test CMA

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Date:	Wed, 07 Mar 2012 11:48:24 +0100
From:	"Michal Nazarewicz" <mina86@...a86.com>
To:	"Barry Song" <Barry.Song@....com>,
	"Cong Wang" <xiyou.wangcong@...il.com>
Cc:	m.szyprowski@...sung.com, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org, workgroup.linux@....com,
	"Barry Song" <Baohua.Song@....com>
Subject: Re: [PATCH v3] MM: CMA: add a simple kernel module as the helper to
 test CMA

> On 03/07/2012 11:14 AM, Barry Song wrote:
>> Any write request to /dev/cma_test will let the module to allocate memory from
>> CMA, for example:
>>
>> 1st time
>> $ echo 1024>  /dev/cma_test
>> will require cma_test to request 1MB(1024KB)
>> 2nd time
>> $ echo 2048>  /dev/cma_test
>> will require cma_test to request 2MB(2048KB)
>>
>> Any read request to /dev/cma_test will let the module to free the 1st valid
>> memory from CMA, for example:
>>
>> 1st time
>> $ cat /dev/cma_test
>> will require cma_test to free the 1MB allocated in the first write request
>> 2nd time
>> $ cat /dev/cma_test
>> will require cma_test to free the 2MB allocated in the second write request

On Wed, 07 Mar 2012 05:14:36 +0100, Cong Wang <xiyou.wangcong@...il.com> wrote:
> Any reason why using /dev not /proc or /sys?

Because /proc is for processes and /sys is for stable, documented APIs.

If anything, debugfs might make some sense, but since the module needs struct
device anyway, it can just register a misc device, which is simpler and does
not require debugfs to be compiled.

-- 
Best regards,                                         _     _
.o. | Liege of Serenely Enlightened Majesty of      o' \,=./ `o
..o | Computer Science,  Michał “mina86” Nazarewicz    (o o)
ooo +----<email/xmpp: mpn@...gle.com>--------------ooO--(_)--Ooo--
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